Huntsman Lake Dam Rehabilitation Project

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Huntsman Lake Dam Rehabilitation Project Huntsman Lake Dredging and Restoration Department of Public Works and Environmental Servcies

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  • 1. HuntsmanLakeDamRehabilitationHuntsmanLakeDredgingandRestorationDepartmentofPublicWorksandEnvironmentalServices FairfaxCounty,VAAFairfaxCounty,VApublicationSeptember2012

2. HuntsmanLakeDamRehabilitationHuntsmanLakeDredgingandRestoration Outline DamRehabilitation Background Majordesignelements Easements Mitigationfortreeandwetlandloss LakeDredgingandRestoration Sedimentation Dredgingoptionsandapproach Lakerestoration TimelineforProjectsandCoordination 3. HuntsmanLakeDamRehabilitationProject Background HuntsmanLakeDamisa41.5feethighearthfilldambuiltin1973asfloodcontroldambytheNaturalResourcesConservationService(NRCS).FairfaxCountyandtheNorthernVirginiaSoilandWaterConservationDistrict(NVSWCD)werethelocalsponsors. ItwasthesecondofsixdamsbuiltbytheNRCSinthePohickCreekwatershed 4. HuntsmanLakeDamRehabilitationProject Background Thedamdrainsanareaof1,482acres(2.3squaremiles) Landuseinthedrainageareais73percentresidentialand22percentwoodlandoropenspace 5. HuntsmanLakeDamRehabilitationProject Background Thedamimpoundsa28.6acrelakeatnormalpool,withafloodwaterretardingpoolareaof60acres HuntsmanLakeDamisregulatedbytheVirginiaDepartmentofConservationandRecreation(DCR),DivisionofDamSafety 6. HuntsmanLakeDamRehabilitationProject Background HuntsmanDamoperatesunderaconditionalOperation&Maintenance(O&M)CertificatefromDCRbecauseits auxiliaryspillwaycanonlyconveyabout50percentoftheflowsfromthedesignstorm. 7. HuntsmanLakeDamRehabilitationProjectBackground In2010,NRCSincollaborationwithFairfaxCountyandNVSWCDinitiatedarehabilitationprojectfortheHuntsmanLakedam FairfaxCountycontractedwithSchnabelEngineeringtoprovideengineeringandancillaryservicesfortheproject Alocaltaskforcewasformedtoprovideinputoncommunityconcerns,andanumberoftaskforcemeetingsandpublicmeetingswereheldin2010and2011 ArehabilitationplanwasdevelopedbyNRCScollaborativelywithFairfaxCountyandNVSWCDandreleasedinSeptember2011 DesignworkbySchnabelEngineeringwasinitiatedshortlyafterthereleaseoftherehabilitationplan,andafinaldesignsubmittedinAugust,2012 8. HuntsmanLakeDamRehabilitationProject Summaryofrehabilitationplan 9. HuntsmanLakeDamRehabilitationProjectMajorDesignElements 10. HuntsmanLakeDamRehabilitationProject riserreplacement 11. HuntsmanLakeDamRehabilitationProject riserreplacement 12. HuntsmanLakeDamRehabilitationProject spillwayrealignmentandarmoring 13. HuntsmanLakeDamRehabilitationProject spillwayrealignmentandarmoring 14. HuntsmanLakeDamRehabilitationProject spillwayrealignmentandarmoring 15. HuntsmanLakeDamRehabilitationProject EasementsApublichearingfortherequiredeasementonLakewoodHillsCommunityAssociation#1propertyisplannedforDecember4,2012 16. HuntsmanLakeDamRehabilitationProject mitigationfortreeandwetlandloss 17. HuntsmanLakeDamRehabilitationProject Summary In2010,NRCSincollaborationwithFairfaxCountyandNVSWCDinitiatedarehabilitationprojectfortheHuntsmanLakedam FinaldesignfortheprojecthasbeencompletedbySchnabelEngineeringandisawaitingapprovalbyNRCSandFairfaxCounty Permitapplicationshavebeenpreparedfortheprojectandwillbesubmittedshortly ApublichearingforaneasementrequiredonLakewoodHills#1HomeownersAssociationpropertyisproposedforDecember4th,2012 MitigationfortreeandwetlandlossasaresultoftheprojectisproposedonthelakeshorelineandonMiddleRunupstreamofHuntsmanBoulevard 18. HuntsmanLakeDredgingandLakeRestoration Background 19. Huntsman Lake Facts Drainage Area = 1,482 acres (2.3 square miles) Lake Surface Area = 28.6 acres Sediment Pool Capacity = 295,000 cubic yards (CY) Current sediment in lake = 65,000 CY Estimated annual sediment load = 2,970 CY 32.5 feet65,000 CY 20. SedimentThickness 21. WaterDepth 22. InactiveDewateringBasin 2011 23. LakeRestorationandDredgingProjectProjectGoals Restoresedimentpoolcapacity Downstreamwaterqualitybenefits Lakewaterquality Esthetics Improvelakewaterqualityandhabitat Providelongtermmaintenanceimprovements 24. Dredging Alternatives1. Mechanically dredge and haul wet2. Drain lake and dry in place before hauling3. Hydraulically dredge and dewater on shore in Geo- textile bags 25. LakeBartonExamplePREDREDGING:Anestimated35,000cubicyardsofsedimentaccumulatedinthelakeformingislandsandreducingwaterlevelstolessthanthreefeetinmostareas. 26. Lake Barton: Pre-Dredging 27. LakeBarton:DredginginProgress 28. LakeBarton:Dredginginprogress 29. LakeBarton:Dredginginprogress 30. Lake Barton: Completed Project 31. OptiontoDrainLakeLake Needwood inMontgomeryCounty,MD 32. OptiontoDrainLake 33. OptiontoDrainLakeLake Needwood inMontgomeryCounty,MD33 34. Huntsman LakePhase 1 Dredging 30,000 Cubic Yards 35. Huntsman LakePhase 2 Dredging up to an additional 35,000 Cubic Yards 36. LakeRestoration Inlakeforebay Wetlandplanting Shorelinestabilization Fishhabitat Fishstocking LakeBarton:FishstockingbyVirginiaGameandInlandFisheriesFishhabitatcreatedfromsalvagedtrees 37. ShorelineRestoration 38. ShorelineRestorationHuntsmanLakeExistingConditions 39. ShorelineProtectionOptions 40. Fish Habitat Structures 41. Huntsman LakeSite Access and Staging Area 42. Huntsman Lake2011 43. HuntsmanLakeDamRehabilitationHuntsmanLakeDredgingandRestorationProjecttimelineandcoordination ProjectagreementbetweenFairfaxCounty,NVSWCDandNRCS(fordamrehabilitation)expectedtobeexecutedbyFebruary/March,2013 Projectbiddingandcontractaward:approximately23months Projectduration:89months Lakewillremaindrainedforentireproject Drawdownwillbecontrolledtoallowfishtomigratedownstreamtothegreatestextentpossible Damrehabilitationanddredgingprojectswillbecoordinatedtominimizethetimelakeisdrained Lakefillingafterprojectcompletionisdependentonrainfallconditions 44. HuntsmanLakeDamRehabilitation HuntsmanLakeDredgingandRestoration Formoreinformationortorequestthisinformationinanalternateformat,calltheStormwaterPlanningDivision,DepartmentofPublicWorksandEnvironmentalServices,FairfaxCounty7033245500 TTY711oremailSWPDmail@fairfaxcounty.gov

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